Circuit Switched(CS) Fallback In(Long Term Evolution )LTE Voice Quality Research

With the rapid development of mobile communication, user demand for data services is goi ng strong, thus, 3GPP has defined evoluting technology of UMTS, which is packet data serviceoriented, and named as Evolved Packet System(EPS). Since the CS domain is disappeared from the EPS network, how to implement the traditional voice business carried out by the CS domain original, has become one of the key issues faced by operators. The circuit switched fallback(CS FB) defined by 3GPP ensure that users are registered in EPS and traditional circuit domain netw ork simultaneously. When a user initiates a voice service, the EPS instructs a user to fall to the ci rcuit domain network and then execute the voice call initiated by the user. Because the support te rminal device for Voice over LTE(Vo LTE) is immature currently, CSFB is a transition program f or Long Term Evolution(LTE) before the VoLTE, and will be exist in a long time. However, the i rrational allocation of the network parameters, the imperfection of the network and terminal capa bilities, and other factors are result in users’ uncomfortable experience in CSFB. In order to enha nce users’ perception in CSFB, voice quality improvement methods of CSFB will be studied in t his thesis.Four scenes of call failure in CSFB will be analyzed in this thesis, and the study will be conducted in four ways: The problems of call blocking. Various call blocking in CSFB will be analyzed, and the signal characteristics and occurrence situation of call blockings will be summarized. On this basis, the solutions to call blockings will be presented. With examining the ways to shorten the time delay, we will propose the optimal solution to shorten the time delay in CSFB, which is based on multi-network and multi-level network element equipment. LTE neighbor cell configuration to 2G.By accurate positioning LTE cell with 2G cell adjacent areas based on the location of CSFB user, accuracy of neighborhood will be raised substantially. To gain an insight into the characteristics of the case in which the paging, signal shift and connection are the worst, the study is executed in the network cell where the signal is the worst. Finally, we examine nine cases to verify the reliability and accuracy of the results.